41. “On the Use of N, N′-Dipyrrolylmethane in Heterocyclic Synthesis. Dipyrrolo [1,2c:2′, 1′e]-2 H-imidazole and its Aromatic Anion”
    Burger, U.; Dreier, F.
    Helv. Chim. Acta 1980, 63, 1190-1197.

The pyrrolate ion (5) is shown to produce N, N′-dipyrrolyl methane (4) when reacted with dichloromethane under conditions of weak counter-ion association. 1-Azoniafulvene ion (13) is suggested to be the key intermediate in this reaction. N, N′-Dipyrrolyl methane (4)undergoes intramolecular oxidative coupling when treated with butyllithium and Cu(II)chloride, yielding the novel ring system of dipyrrolo [1,2c: 2′, 1′e]-2 H-imidazole (3). The latter upon reaction with methyl lithium forms the Hückel-aromatic anion 2. Solutions of the lithium salt are stable for several days. Reaction of the dianion of 2,2′-bipyrrole (11) with dichloro-methane does not produce 3, but a pyrrolophane-type dimer (12) having its two anticoplanar N, N′-bipyrrolediyl subunits arranged in a double layer and joined by a methylene group on each side.

DOI : 10.1002/hlca.19800630510